1. Field of the Invention
This invention relates to a numerical controlling unit that accelerates and/or decelerates a feeder-driving system.
2. Description of the Related Art
In general, vibration is generated while a feeder-driving system in a machining tool or the like is accelerated or decelerated. This is caused by generation of a vibrating (exciting) force when supply of an acceleration is started or stopped.
During a machining operation to a metallic work or the like, the vibration may greatly affect precision of the machined surface. Thus, it is necessary that the vibration be controlled within a predetermined permissible range. Thus, the value of an acceleration itself is set lower. This means that a time necessary for the machining operation may not be shortened.
In addition, if an accelerating step and a decelerating step are repeated in the machining operation, it is possible that the vibration is not damped down but continues for a longer time. This may be caused by that a subsequent vibration is generated by a subsequent acceleration controlling step before a (previous) vibration generated by a (previous) acceleration controlling step is damped down. In the conventional numerical controlling unit, it is just an accident whether a vibration is increased or reduced by successive acceleration controlling steps.
On the other hand, as means for controlling the vibration, there are known various types of vibration-damping units. The vibration-damping units can damp the vibration by generating another vibrating force in a direction effective for damping the vibration.
Regarding a machining operation to a metallic work or the like, in order to shorten a machining time, it is necessary to effectively damp vibration that may be generated by supply of an acceleration. If vibration at each acceleration controlling step is effectively damped, the possibility that the vibration is increased may be remarkably reduced, even when there are successive acceleration controlling steps.
The above subject can be solved by attaching a known vibration-damping unit to the numerical controlling unit. However, the vibration-damping unit and the numerical controlling unit are not united completely, and thus there are problems of setting-up-space and of cost.
Therefore, the object of this invention is to provide a numerical controlling unit that can effectively damp vibration that may be generated when a feeder-driving system in a machining tool or the like is accelerated or decelerated.
To achieve the above object, this invention is characterized by following features. That is, this invention is a numerical controlling unit that accelerates or decelerates a feeder-driving system comprising: an acceleration setting part that can set a volume and a timing of an acceleration that should be supplied to the feeder-driving system, based on a predetermined target condition; and a controlling part that can supply the acceleration set by the acceleration setting part to the feeder-driving system; wherein the acceleration setting part is adapted to set: a first acceleration that starts to be supplied at a timing of starting to accelerate; and a second acceleration (whose direction is the same as the first acceleration) that has a volume and that starts to be supplied overlappedly with the first acceleration at a timing, the volume and the timing being determined so as to damp vibration of the feeder-driving system that is generated by starting to supply the first acceleration.
According to the feature, the first acceleration and the second acceleration are paired with each other, so that the second acceleration having the volume starts to be supplied at the timing in order to damp the vibration of the feeder-driving system that is generated by starting to supply the first acceleration. That is, the vibration caused by a vibrating force accompanied with starting to supply the first acceleration is canceled out by another vibration caused by another vibrating force accompanied with starting to supply the second acceleration. Thus, the vibration is effectively damped down when starting to accelerate the feeder-driving system based on the predetermined target condition.
In detail, the timing at which the second acceleration starts to be supplied is a moment wherein an amplitude of the vibration of the feeder-driving system is lowered to zero. At that time, the vibration accompanied with starting to supply the first acceleration and the vibration accompanied with starting to supply the second acceleration are summed up in a relationship of opposite phase, so that amplitudes of the two vibrations are canceled out by each other.
In order to immediately damp down the vibration caused by a vibrating force accompanied with starting to supply the first acceleration, it is preferable that the second acceleration starts to be supplied at a moment wherein an amplitude of the vibration of the feeder-driving system returns to zero at first.
In addition, theoretically, the volume of the second acceleration is the same as the volume of the first acceleration. However, the vibration caused by a vibrating force accompanied with starting to supply the first acceleration may be slightly damped down even for half of a period thereof. If such a slightly damped volume is taken into consideration, it is preferable that the volume of the second acceleration is smaller than the volume of the first acceleration by the slightly damped volume.
In addition, in general, the vibration of the feeder-driving system may be generated based on a natural frequency of the feeder-driving system. That is, the timing at which the second acceleration starts to be supplied is dependent on the natural frequency of the feeder-driving system.
Thus, for example, the acceleration setting part has a storing part that can store a natural frequency of the feeder-driving system, and a timing determining part that can determine the timing at which the second acceleration starts to be supplied based on the natural frequency of the feeder-driving system.
In the case, it is preferable that the natural frequency of the feeder-driving system is precisely measured in advance and that the measured frequency is stored in the storing part.
Alternatively, the natural frequency of the feeder-driving system can be obtained via a theoretical calculation using rigidity of the feeder-driving system and a feeder-part (movable-part) weight of the feeder-driving system.
Thus, for example, the acceleration setting part may further have a calculating part that can calculate the natural frequency of the feeder-driving system based on the rigidity of the feeder-driving system and the feeder-part weight of the feeder-driving system.
In the case, the natural frequency of the feeder-driving system obtained by the calculating part is stored in the storing part.
In fact, one feeder-driving system that is to be controlled by one numerical controlling unit may often have a plurality of axes. In such a case, it is more effective that the invention is applied to an axis having the lowest natural frequency.
The idea of supplying paired two accelerations to damp down the vibration as described above is effective when ceasing to accelerate the feeder-driving system.
That is, it is preferable that the acceleration setting part is adapted to further set: a fourth acceleration (whose direction is opposite to the first acceleration and the second acceleration) that starts to be supplied at a timing of ceasing to accelerate; and a third acceleration (whose direction is opposite to the first acceleration and the second acceleration) that has a volume and that starts to be supplied at a timing before supplying the fourth acceleration, the volume and the timing being determined so as to generate vibration of the feeder-driving system that can be damped by starting to supply the fourth acceleration overlappedly with the third acceleration.
According to the feature, the third acceleration and the fourth acceleration are paired with each other, so that the third acceleration having the volume starts to be supplied at the timing in order to generate the vibration of the feeder-driving system that can be damped by starting to supply the fourth acceleration overlappedly with the third acceleration. That is, the vibration caused by a vibrating force accompanied with starting to supply the third acceleration is canceled out by another vibration caused by another vibrating force accompanied with starting to supply the fourth acceleration. Thus, the vibration is effectively damped down when ceasing to accelerate the feeder-driving system based on the predetermined target condition.
Similarly, the idea of supplying paired two accelerations to damp down the vibration is effective when starting to decelerate the feeder-driving system as well.
That is, this invention is a numerical controlling unit that accelerates or decelerates a feeder-driving system comprising: an acceleration setting part that can set a volume and a timing of an acceleration that should be supplied to the feeder-driving system, based on a predetermined target condition; and a controlling part that can supply the acceleration set by the acceleration setting part to the feeder-driving system; wherein the acceleration setting part is adapted to set: a first acceleration that starts to be supplied at a timing of starting to decelerate; and a second acceleration that has a volume and that starts to be supplied overlappedly with the first acceleration at a timing, the volume and the timing being determined so as to damp vibration of the feeder-driving system that is generated by starting to supply the first acceleration.
According to the feature, the first acceleration and the second acceleration are paired with each other, so that the second acceleration having the volume starts to be supplied at the timing in order to damp the vibration of the feeder-driving system that is generated by starting to supply the first acceleration. That is, the vibration caused by a vibrating force accompanied with starting to supply the first acceleration is canceled out by another vibration caused by another vibrating force accompanied with starting to supply the second acceleration. Thus, the vibration is effectively damped down when starting to decelerate the feeder-driving system based on the predetermined target condition.
In addition, the idea of supplying paired two accelerations to damp down the vibration is effective when ceasing to decelerate the feeder-driving system as well.
That is, it is preferable that the acceleration setting part is adapted to further set: a fourth acceleration (whose direction is opposite to the first acceleration and the second acceleration) that starts to be supplied at a timing of ceasing to decelerate; and a third acceleration (whose direction is opposite to the first acceleration and the second acceleration) that has a volume and that starts to be supplied at a timing before supplying the fourth acceleration, the volume and the timing being determined so as to generate vibration of the feeder-driving system that can be damped by starting to supply the fourth acceleration overlappedly with the third acceleration.
According to the feature, the third acceleration and the fourth acceleration are paired with each other, so that the third acceleration having the volume starts to be supplied at the timing in order to generate the vibration of the feeder-driving system that can be damped by starting to supply the fourth acceleration overlappedly with the third acceleration. That is, the vibration caused by a vibrating force accompanied with starting to supply the third acceleration is canceled out by another vibration caused by another vibrating force accompanied with starting to supply the fourth acceleration. Thus, the vibration is effectively damped down when ceasing to decelerate the feeder-driving system based on the predetermined target condition.